This invention relates to an intrusion warning wire fence comprising at least one tubular wire which is preferably of metal, or of plastics, glass-fibre reinforced resin, or the like, said tubular wire having substantially the same appearance and, at least apparently, the same mechanical barrier function as the normal wires or as other normal wires possibly included in the same fence, and loosely containing one or more electrical and/or optical conductors, preferably optical fibres, connected to a warning system responsive to any breagage and/or variation of conduction capability of said conductors.
Intrusion warning wires fences of this type have been illustrated in the U.K. Patent Application No. GB-A-2060966.
This invention aims to further increase the protection efficiency of the wire fences of the specified type, and particularly to eliminate any possibility to get over the fence by climbing thereon.
For this purpose, the wire fence described above, according to the invention, is characterized in that at least a tubular wire containing one or more electrical and/or optical conductors is weakened by means of notches or grooves, and/or it is made to look like a barbed wire by arranging suitable barbs thereon.
The weakening notches or grooves in the tubular wire containing the electrical and/or optical conductor or conductors can extend either transversely, circumferentially, or over an arc of the circumference of the tubular wire, or they can extend longitudinally or helically thereon.
The sharp barbs added to obtain the appearance of barbed wire on the tubular wire containing the electrical and/or optical conductor or conductors, can be either conventional wire barbs, or barbed tapes provided with pointed and/or cutting barbs and transversely folded around the tubular wire.
The barbed tubular wires, formed by folding a barbed tape around a tubular wire, may be mechanically weakened by notches or grooves affecting only the thickness of the barbed tape, or both the thickness of the barbed tape and a part of the thickness of the wall of the tubular wire.
According to a further characteristic of the invention, a tubular wire containing the electrical and/or optical conductor(s) and weakened and/or made like barbed wire, is coiled so as to form a concertina wire. Such a concertina wire can be accommodated between two V-arranged arms directed one inwards and the other outwards of the fence, respectively, and arranged on the tops of the poles existing between the individual sections of the fence.
Obviously, said concertina wire of weakened and/or barbed tubular wire containing one or more electrical and/or optical conductors can also be used alone and can constitute by itself the intrusion warning wire fence described in the preamble.